Purpose: Recognizing canal configuration is necessary for a correct endodontic therapy and having no information about canal configuration causes failure in therapy. Since one of the most effective factors in canal configuration is race، we decided to have a laboratory and clinical research in Isfahan. The aim is to recognize canal configuration of the mandibular first premolar and compare the clinical and laboratory results. Methods & Materials: 1- Laboratory study (Invitro): At first we selected 127 mandibular first premolar، then we disinfected them in CLONA 5.25%. We made a correct access cavity on the teeth.In order to vacate pulp tissue in chamber and canals, we placed them in H2O2 35% for 15 days. Then we placed them in HNO3 5% for 3 days to be decalcified. Then we used 70%, 90%, 100% isopropyl alchole to dehidrate the teeth. After the above proccesses we injected India ink in -1.8 P, in canals and sealed access cavity by Zonaline cement, we used the teeth in Metyle Salicylate to make clear. Then, we studied canal configuration. 2- Clinical study (Invivo): In this study we selected 125 mandibular first premolar treated in post graduate and under graduate departments of Isfahan University school of Dentistry. Then we studied every radiograph using a negatoscope, and the data were analysed.

Conclusion: The out coming results of this study are different from other researches. Perhaps the differences are caused by some factors such as race and method. Also the clinical results are too different from laboratory results which could be due to method. The labratory study is more exact.